1. Technical Field
The present invention relates to an electronic device, and a manufacturing method of an electronic device, in which a first substrate including a drive element formed thereon is bonded to a second substrate, in a state of a bonding resin being interposed therebetween.
2. Related Art
An electronic device includes a drive element such as a piezoelectric element that is deformed in response to an applied voltage, and the electronic device is applied to various types of devices, sensors, or the like. For example, a liquid ejecting apparatus ejects various types of liquid from a liquid ejecting head using the electronic device. Examples of the liquid ejecting apparatus include an image recording apparatus such as an ink jet printer and an ink jet plotter, but in recent years, the liquid ejecting apparatus has also been applied to various manufacturing apparatuses, by taking advantage of features that a very small amount of liquid can be accurately landed at a predetermined position. For example, the liquid ejecting apparatus has been applied to a display manufacturing apparatus that manufactures a color filter for a liquid crystal display, or the like, an electrode forming apparatus that forms electrodes in an organic electro luminescence (EL) display, a field emission display (FED), or the like, and a chip manufacturing apparatus that manufactures a bio-chip (a biochemical element). Then, a recording head for the image recording apparatus ejects liquid ink, and a color material ejecting head for the display manufacturing apparatus ejects respective color material solutions of Red (R), Green (G), and Blue (B). Further, an electrode material ejecting head for the electrode forming apparatus ejects liquid electrode materials, and a bio-organic material ejecting head for the chip manufacturing apparatus ejects a bio-organic material solution.
The liquid ejecting head includes an electronic device in which a flow path substrate including a pressure chamber formed thereon in communication with a nozzle, a piezoelectric element (a type of a drive element) causing a pressure fluctuation in liquid inside the pressure chamber, a sealing plate (or also referred to as a protection substrate) provided and spaced from the piezoelectric element, and the like are stacked. In recent years, a technique of providing a drive circuit related to the driving of an actuator such as a piezoelectric element on a sealing plate has also been developed. Then, a technique is proposed in which this substrates are bonded with each other by adhesive (adhesive resin) made of photosensitive resin in a state where there is a space therebetween. In addition, a structure is adopted in which substrates are stacked by a photosensitive resin in order to correspond to the high density and miniaturization of a wiring, in a semiconductor package of a micro electro mechanical systems (MEMS) such as various sensors. For example, in an ink jet printer which is disclosed in JP-A-2014-51008, a plurality of piezoelectric elements as a drive element are formed on a vibration plate of a flow path unit, and the vibration plate is bonded to a substrate (a driver IC) including a drive circuit formed therein, in a state of the piezoelectric element and bump electrodes or the like for driving the piezoelectric element being interposed therebetween. Further, sealing material made of insulating material such as synthetic resin is arranged along the bump electrode, and a space that accommodates a piezoelectric element or the like is hermetically sealed by the sealing material and is blocked from the atmosphere. This sealing material also functions as adhesive (bonding resin) for bonding the substrates to each other.
However, in the configuration in which the substrates are bonded to each other in a state of structures such as the piezoelectric element and the bump electrodes for driving the piezoelectric element being interposed therebetween, an unevenness (relief) caused by these structures is generated on the bonding surface of the substrate. The bonding resin such as the afore-mentioned sealing member is designed to have a height (a thickness during application) aligned to the largest bump electrode, among the structures. However, since there is a relief on the bonding surface of the substrate, there is a need for applying a pressure to some extent when bonding the substrates to each other in order to fill this relief. In this case, since there is a space for accommodating the piezoelectric element and the like between the substrates, there are cases where deformation such as warpage or distortion occurs in the substrate, with the bump electrode and the bonding resin as a reference. If the substrate is deformed, there is a possibility in that the malfunction such as contact failure occurs in the bump electrode.